1. Field of the Invention
The present invention relates to an exposure apparatus used in a lithography process for manufacturing micro devices such as semiconductor devices, liquid crystal display devices, plasma display devices, and thin film magnetic heads and, more particularly, to a projection exposure apparatus that transfers a mask pattern onto a substrate via a projection optical system and to a manufacturing method of such an exposure apparatus.
2. Related Background Art
In the lithography process for manufacturing semiconductor devices etc. are used projection exposure apparatuses of one-shot exposure (stationary exposure) type or of scanning exposure type (e.g., projection exposure apparatuses of step-and-repeat type, so-called steppers; or projection exposure apparatuses of step-and-scan type, so-called scanning steppers). The projection exposure apparatus has a projection optical system that projects the mage of a pattern on a reticle as a mask onto a photosensitive substrate (a wafer, a glass plate, etc.), illuminates the reticle with exposure light, and exposes the substrate with the exposure light passing through the projection optical system.
With respect to the exposure apparatus, along with, for example, the miniaturization of patterns transferred onto the wafer, a higher exposure accuracy is not required. To address the requirement, the numerical aperture of the projection optical system of the projection exposure apparatus has become larger to enhance the resolution of the projection optical system, and at the same time the wavelength of the exposure light has been made to be shorter. Accordingly, the projection optical system has become large-sized due to the enlargement of the numerical aperture, and at the same time, the configuration of the projection optical system has become complicated due, for example, to the use of refractive members made of optical materials with high transmittance relative to short wavelength exposure light and to the use of reflective members.
On the other hand, in each of the reticle stage system positioning the reticle and the wafer stage system two-dimensionally moving the wafer is adopted a configuration that enables high-precision positioning or high-precision scanning. Conventional projection exposure apparatuses have been manufactured by, after fixing the projection optical system on a certain frame mechanism, framing the reticle stage system and the wafer stage system with a predetermined positional relationship with reference to the projection optical system.
Further, in the case of using ultraviolet light as the exposure light, it is known that the ultraviolet light chemically reacts with a small amount of organic substances, etc. residing in the air, and fogging materials are generated onto the surfaces of lenses, etc. constituting the projection optical system. The fogging materials cause the decrease of the transmittance of the projection optical system. In consideration of this, the organic substances, etc. have been conventionally removed from the gas surrounding the projection optical system by using a chemical filter and the like.
With respect to recent projection exposure apparatuses, to further enhance the resolution addressing further miniaturization of semiconductor integrated circuits, etc., KrF excimer lasers (of 248 nm wavelength), as the exposure light source, are gradually being replaced with ArF excimer lasers of vacuum ultraviolet region (of 193 nm wavelength), and further, the use of F2 lasers (of 157 nm wavelength) and of Kr2 lasers (of 146 nm wavelength) of further shorter wavelength as the exposure light source is also studied.
When vacuum ultraviolet light of a wavelength of about 200 nm or less is used as the exposure light, the absorption (attenuation) amount of the exposure light by the air (in particular, by oxygen) becomes greater, compared with the use of far ultraviolet light. To address this problem, it is preferable that high-purity gas (purge gas), e.g., nitrogen gas or helium gas, which has high transmittance relative to ultraviolet light and from which impurities such as organic substances and oxygen are removed is supplied into the optical path, in the projection exposure apparatus, through which the exposure light passes. Further, with respect to projection exposure apparatuses using exposure light of ultraviolet region, optical materials with high transmittance relative to the exposure light, e.g., synthetic quartz and fluoride (CaF2), are used as the refractive members of the projection optical system.
However, even when optical materials with high transmittance relative to the exposure light and purge gas are used, the transmittance of the projection optical system inevitably decreases to some extent. For instance, when fogging materials are generated on the optical members constituting the projection optical system because of a small amount of organic substances, etc. remaining in the purge gas, the transmittance of the projection optical system may decreased to a level below a permissible level. To clean, replace, or readjust the fogged optical members under those circumstances, it may be required to dismount the projection optical system from the main body of the exposure apparatus. Also, it is preferable that when the readjustment etc. of the projection optical system requires a considerable time, another projection optical system of which optical adjustment, etc. have been completed, in place of the former, be mounted on the main body of the exposure apparatus to prevent the decrease of the operation rate of the projection exposure apparatus. In addition, when, other than the transmittance decrease, a predetermined aberration of the projection optical system deteriorates down to a level below a permissible level because of, e.g., outside vibration, etc., it may be required to dismount and readjust the projection optical system or to, alternatively, replace it with another one.
However, with respect to the conventional projection exposure apparatus, a wafer stage system, etc. should be dismounted before dismounting the projection optical system, and thus it is required to disassemble substantially the main parts of the projection exposure apparatus. Accordingly, the disassembling operations of the projection exposure apparatus become complicated and require a long time. In addition, the conventional projection exposure apparatus has many units that are assembled with reference to the projection optical system. Thus, when mounting the projection optical system of which adjustment have been completed on the main body of the exposure apparatus, a great many operations must be executed, and, as a disadvantageous result, the maintenance costs increase along with the delayed restart of the projection exposure apparatus, i.e., the decrease of the operation rate thereof.
It is an object of the present invention to provide a projection exposure apparatus of which projection system can be easily dismounted or replaced. Further, it is another object to provide a projection exposure apparatus of which adjustment can be easily performed. Further, it is still another object to provide a manufacturing method of a projection exposure apparatus of which maintenance etc. can be easily performed.
A first projection exposure apparatus according to the present invention is a projection exposure apparatus by which an object is exposed with an exposure beam via a projection system, which is provided with a base member and with a frame mechanism slidable on the base member, and in which the projection system is mounted on the frame mechanism. Thus, by sliding the frame mechanism, dismounting, replacing, etc. of the projection system can be performed extremely easily.
Further, a second projection exposure apparatus according to the present invention is a projection exposure apparatus by which an object is exposed with an exposure beam via a projection system and which is provided with a base member, with a frame mechanism on which the projection system is mounted and which is disposed on the base member via a leg portion, and with a stage system, slidable in a predetermined direction, at least of which supporting portion is positioned, on the base member, inside of the leg portion and which drives the object.
Relative to the second projection exposure apparatus, as a first method, after sliding the stage system in the predetermined direction and pulling it out, by sliding the frame mechanism, still carrying the projection system, in the predetermined direction, the projection system can be easily dismounted. Also, as a second method, by directly sliding the frame mechanism in the opposite direction to the predetermined direction, the projection system can be easily dismounted. Next, after, for example, readjusting the projection system on the frame mechanism or replacing it with another projection system of which adjustment has been completed, by executing a sequence reverse to that of the first or second method, the frame mechanism, i.e., the projection system, can be easily positioned again to the exposure position.
Relative to the above, as shown in FIG. 4 by way of example, the leg portion of the frame mechanism may be constituted of three leg portions (14A-14C), each of which is positioned substantially at each apex of a triangle; and in this case width D1 of the supporting portion (22A-22C) of the stage system is preferably smaller than distance D2 between a prescribed pair of neighboring leg portions (14A and 14B) among the three leg portions of the frame mechanism. With this configuration, the above-described first method can be used with the stage system being slid and pulled out in the direction of the two leg portions (14A and 14B).
Further, as shown in FIG. 5 as another example, the leg portion of the frame mechanism may be constituted of four leg portions (14A-14D), each of which is positioned substantially at each apex of a rectangle; and in this case the width of the supporting portion (22A-22D) of the stage system is preferably smaller than the distance between a prescribed pair of neighboring leg portions (14C and 14D) among the four leg portions of the frame mechanism. With this configuration, because the stage system can be slid in the direction (B4) of the two leg portions (14C and 14D), the above-described second method can be used with the frame mechanism being slid in the direction (B1) opposite to the former.
Further, it is preferable that air pads for jetting compressed gas are provided on the bottom surface of the leg portion of the frame mechanism. Through this, the frame mechanism can be smoothly slid on the base member.
Next, a manufacturing method of a projection exposure apparatus, according to the present invention, is a manufacturing method of a projection exposure apparatus which exposes an object with an exposure beam via a projection system; and comprises a first step of disposing a frame mechanism that supports the projection system on a predetermined base member via a leg portion and a second step of disposing, inside of the leg portion on the base member, a stage system that drives the object, in a state that the stage can be slid in a predetermined direction. By this manufacturing method, the projection exposure apparatuses according to the present invention can be effectively manufactured.
Relative to the above method, if the above-described first method is applied when the projection system is replaced, after carrying, along the predetermined direction, the stage system out of the base member, the frame mechanism can be carried out of the base member, in a state that the frame mechanism is supporting the projection system.
Further, if the above-described second method is applied when the projection system is replaced, with the frame mechanism being moved, on the base member, in the direction opposite to the predetermined direction in a state that the frame mechanism is supporting the projection system, the frame mechanism can be carried out of the base member.
As can be seen from the above, a projection exposure apparatus which facilitates the dismount, replacement, etc. of its projection system (projection optical system) can be realized. By this, replacement of a projection system can be completed in a short time period not only in a projection exposure apparatus manufacturing plant but also at a point of delivery (device manufacturing plant, etc.); and thus manufacturing costs of the projection exposure apparatus can be decreased, and the operation or maintenance costs thereof can also be decreased. Further, the rate of the projection exposure apparatus, i.e., the productivity of device manufacturing process can also be improved.